Have you ever wondered what goes on behind the scenes of live streaming? Well, different types of technologies come together to deliver a highly high-quality video experience to viewers. Among them, encoders play a vital role. Encoding is a process of converting video file from one another, which ensure smooth video playback regardless of the network; at times, you have to create different bitrate or video qualities to give an optimal experience to viewers. When it comes to configuring their encoder settings, broadcasters have a lot of choices. You might have heard about Constant Bitrate (CBR) and Variable Bitrate (VBR) as the two prominent types of encoding. What are they, and how do they differ? Which one should you use? The blog has covered all your answers about CBR vs VBR. So, let’s get started.

Key Takeaways:

What is CBR?

There are two types of bit rate, Variable & Constant. Constant bit is CBR, which helps to maintains a consistent bit rate throughout the entire playback of the video. This makes videos easy to play and quick to load, since everything is constant from start to finish. It also helps to transmit data at a constant rate, as the name suggests. When it comes to encoding, it means using an encoder that outputs data at a constant rate. As a result, it is not responsive to the complexity or size of the files it processes. These variables are irrelevant to CBR, and the output remains constant. These consistencies offered by CBR make it perfect for real-time video encoding situations. However, it is not suited for storing data.

CBR Key Characteristics

Fixed Bitrate:

• Keeps the same bitrate throughout the entire timeframe
• Requires the same data quantity every second regardless of how complicated the scene is.
• Consistent bandwidth used over time for playback at any given moment.

Predictable Preformance Quality:

• Maintains the same quality level across different scenes.
• Ensures dependable streaming quality when broadcasting live.
• Removes quality changes that may disrupt or negatively affect the viewing experience.

Higher File Sizes:

• Often leads to increased file size relative to VBR hypothesi.
• Assigns highest bitrate possible to basic scenes not needing that much.
• Data usage is inefficient in general.

Best for Live Streaming:

• Ideal for applications requiring real-time operations such as live streaming.
• OBS Studio tends to employ CBR for live-streaming sessions with low latency.
• Preferred/commonly adopted by streaming services due to constant bitrate requirement.

What is VBR?

It is a variable bit rate or Video Bitrate. This generally determines the size and quality of video and audio files: the higher the bitrate, the better the rate, and the larger the file size because file size = bitrate (kilobits per second) x duration. Usually, 1 byte per second (1 b/s) corresponds to 8 bit/s. Depending on the level of detail needed, it uses as a dynamic bit rate that changes throughout playback. Slow live streaming scenes have fewer bits than fast-paced, action-packed scenes. Moreover, VBR is generally tricky for devices to playback – since the bit rate is constantly changing. It offers high- quality video quality without larger file sizes. It is best used for videos with either progressive downloads (like on YouTube or Vimeo) or direct downloads.

VBR Key Characteristics

Dynamic Bitrate Allocation:

• Changes bitrate automatically depending on how complicated the scene is.
• Adds more bits to the detailed scenes and the action sequences.
• Uses fewer bits on simple and static scenes.

Efficient Compression:

• Improves the ratio of quality and size of bits used.
• Maintains the visual quality while reducing the overall file size.
• Distribution of all data throughout the video intelligently.

Scene-Based Quality Optimization:

• Complicated scenes get more data to achieve higher quality, higher detail video.
• Simpler scenes that use less data have adequate quality maintained.
• A balanced tradeoff in quality and efficiency.

Ideal for On-Demand Content:

• Best for scheduled recordings as well as content available on demand.
• Achieves the best possible results using two-pass VBR encoding.
• Stored content is easier to work with than live streaming.

Types of Video Bitrate

There are three types of VBR, such as _ Quality VBR, Unconstrained VBR and Constrained VBR,

• Quality VBR is designed to use as a single-pass encoding, which help to encode the data by using a high-quality for the output as a guiding light.
• Unconstrained VBR is designed to use multi-pass encoding. It helps broadcasters to encode the data using a set bitrate of your choosing as a guiding light. It treats this bitrate as the desired average and seeks the highest possible streaming quality across data segments while maintaining that average.
• Constrained VBR uses multi-pass encoding to encode the data using a set maximum bitrate and maximum buffer window as a guiding light. It uses these values to determine how to encode the da

            Comparison Between constant bit rate vs variable bit rate

CBR

• Fixed quality.
• Constant bitrate is perfect for time-sensitive streaming.
• Guaranteed higher quality files.
• Produces consistent results (i.e. if you set it to 1500 kbps, your bitrate will remain at 1500 kbps)
• Quicker encoding.
• Historically popular
• Ideal setting for live stream encoding
• Well-suited for multimedia encoding
• Widely compatible

VBR

• Smaller file sizes.
• Varibale Bitrate is ideal for transcoding without time constraints.
• More efficient use of storage space.
• Does not negatively impact video quality.
• Capable of producing higher-quality streams
• Best-suited for VOD transcoding.
• Minimal reduction in quality.
• Does not negatively impact video quality.
• Possibly more limited support.

CBR VS VBR Which is Better Quality? Which Should I Pick?

CBR is more consistent and reliable for time-sensitive encoding, while VBR produces higher-quality results. For live streaming, you can consider VBR. It is the best for on-demand video uploads. Constant bit rate (CBR) and variable bit rate (VBR) both are compression and transmission techniques, which are widely used.

Conclusion

CBR and VBR are play an essential role in live video streaming process, which help to encode the data by using a high-quality for the output as a guiding light.  Depending your streaming needs, you can choose anyone of them. The bottom line is that CBR is more consistent and reliable for time-sensitive encoding, and VBR produces higher-quality results. CBR is the best choice for live streaming, while restricted VBR is the best choice for on-demand video uploads.

For a comprehensive streaming setup, consider factors beyond just bitrate encoding, including bitrate vs resolution balance, streaming protocols, and hardware encoder options to create the optimal streaming experience for your audience.